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Second-born twin faces doubled risk of death

By Roxanne Khamsi

Second-born twins are more than twice as likely to die during or shortly after vaginal delivery compared to their first-born siblings, a new study reveals.

The analysis of nearly 1400 twin deliveries found that the second-born babies died more frequently from complications such as breech birth and premature detachment of the umbilical cord. Based on this finding, doctors suggest that delivering more twins by planned caesarean section might help reduce the risk of perinatal death.

Gordon Smith at the University of Cambridge in the UK, and colleagues, analysed data from 1377 twin pregnancies between 1994 and 2003 in which one of the infants died during or immediately after birth.

They discovered a significant difference in risk among twins born at term – after 36 weeks of gestation. Among those born at term, 53 first twins did not survive, compared with 124 second-born twins. The analysis showed that the latter group had 2.3 times the risk of dying during delivery.

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Complications such as breech birth and infection were partly to blame for this increased risk, says Smith.

Premature twins

Smith adds that second-born twins appear four-times as likely as their first-born counterparts to die from oxygen deprivation during birth. In some cases, the umbilical cord connecting the second twin to the oxygen-supplying placenta sometimes detaches and is delivered before the baby, Smith explains.

Previous research has shown that second-born twins delivered at term have a one in 250 chance of dying during or shortly after labour.

Smith’s team found that birth order had no effect on the risk of survival among prematurely born twins. According to Smith this is because premature twins have an extremely high mortality risk during delivery, which made it statistically unlikely that birth order would stand out as a major cause of death.

Delivery at around full term by planned caesarean section could help avoid second twins from dying, Smith suggests. Preliminary studies have indicated that twins delivered in this way have a slightly better chance of survival.